Add test

Author: wooorm

index.js

@@ -67,27 +67,20 @@ function attacher(options) {
         ? lowlight.highlight(lang, toText(parent), options)
         : lowlight.highlightAuto(toText(parent), options)
     } catch (error) {
-      if (
-        error &&
-        settings.ignoreMissing &&
-        /Unknown language/.test(error.message)
-      ) {
-        return
+      if (!settings.ignoreMissing || !/Unknown language/.test(error.message)) {
+        throw error
       }
 
-      throw error
+      result = {}
     }
-    
-    if (!lang) {
-      if (result.language) {
-        props.className.push('language-' + result.language)
-      } else {
-        // result.value is empty when highlightjs cant autodetect language
-        result.value = node.children
-      } 
+
+    if (!lang && result.language) {
+      props.className.push('language-' + result.language)
     }
 
-    node.children = result.value
+    if (result.value) {
+      node.children = result.value
+    }
   }
 }
 

test.js

@@ -290,6 +290,16 @@ test('highlight()', function (t) {
     'should not highlight plainText-ed languages'
   )
 
+  t.equal(
+    rehype()
+      .data('settings', {fragment: true})
+      .use(highlight, {subset: ['cpp']})
+      .processSync(`<pre><code>def add(a, b):\n  return a + b</code></pre>`)
+      .toString(),
+    '<pre><code class="hljs language-cpp"><span class="hljs-function">def <span class="hljs-title">add</span><span class="hljs-params">(a, b)</span>:\n  <span class="hljs-keyword">return</span> a + b</span></code></pre>',
+    'should not remove contents'
+  )
+
   t.equal(
     rehype()
       .data('settings', {fragment: true})